Machine for cleaning sand castings and recovery of components



Nov. 17,1970 H. w. STEBBINS r AL 3,540,156

MACHINE FOR CLEANING SAND CASTINGS AND RECOVERY OF COMPONENTS Filed Dec. 13, 1967 B s Tb. 1: NE 6d Wm: r1. [.WJG mm HH 4 United States Patent 3,540,156 MACHINE FOR CLEANING SAND CASTINGS AND RECOVERY OF COMPONENTS Hardy W. Stebbins and Richard C. Kanouse, Mishawaka, Ind, assignors to The Wheelabrator Corporation, Mishawaka, Ind., a corporation of Delaware Filed Dec. 13, 1967, Ser. No. 690,247 Int. Cl. B24c 3/26 U.S. CI. 51-13 Claims ABSTRACT OF THE DISCLOSURE Unitary apparatus for rough cleaning and finish cleaning work pieces such as foundry sandeastings receives sand casting molds in sequentially introduced loads direct from the molding floor. In a first rough cleaning operation during which the apparatus operates continuously to tumble the sequentially introduced loads of molds to remove sand and debris from the work pieces contained therein, the sand and debris is continuously conveyed to a separator system in which a first stage removes trash and unwanted debris and a second stage utilizes magnetic separation means to recover shot blasting media while discharging foundry sand externally of the separator. The shot blasting media returns to the conveyor system. During a subsequent finish cleaning operation in which the accumulated loads of work pieces are subjected to a finish cleaning operation by centrifugal blast means, the residual sand and spent and reusable blast media are sent by the conveyor to another separator system, the first named system having then been rendered inoperative by operation of a gate which precludes flow of material thereinto. At the third separator, sand and spent blast media are discharged externally by the separator and reusable media flows to the blast machine.

This invention relates to a machine for sequentially rough cleaning and finish cleaning work pieces, such as sand castings which may be delivered to a machine directly from the molding floor.

The finish cleaning operation is conducted by centrifugal blast means incorporated within the principal machine, said blast means operating to bombard the work pieces with metallic shot or grit or other magnetic metal. It has previously been the practice to effect some degree of precleaning of the castings to prevent overloading of the cleaning apparatus and to insure clean separation of the residual sand from the metallic shot to enable reuse of the shot without sand being present in such amounts as would cause excessive wear of the blast machines and thus shorten the useful life thereof.

We have found that by embodying a preliminary trash separation and magnetic separation in combination with the blast cleaning means, together with means for selectively cutting such separators into or out of the operational sequence of the machine, it has been possible to adapt the cleaning machine for handling large quantities of sand castings as they are received from the molding floor. In the practice of this invention, the mold jackets may be and preferably are removed at the machine whereupon the core material and substantially all of the mold sand passes with the castings into the machine. This meth- 0d of operation offers a substantial improvement, from the standpoint of efficiency, over present foundry practice in which the mold jackets are removed on the molding floor and as much of the molding sand and core material as possible are removed before the castings are introduced into a machine for cleaning.

In a typical cycle of operation representative of the practice of this invention, full molds are delivered to the loading equipment for the cleaning machine, as by convenice tional roller conveyors, from which the molds are tipped gravitationally into the loader. During this operation, mold boards are automatically stripped from the molds by conventional apparatus well known in modern foundry practice. The contents of the molds, including substantially all of the sand, enters the machine.

During the initial stage of loading and operation, the machine is operated only to tumble the castings, The sand and debris, released from the castings during the free tumbling period, are drained through a foraminous floor and collected for conveyance by means including a by-pass gate to a conventional rotary screen separator whereby substantially all of the trash and non-usable debris is removed from the sand. The sand is then passed directly to a second processing stage which embodies a magnetic drum separator wherein the residual magnetic abrasive or shot is separated from the sand and recycled to the machine. The sand is discharged externally of the separator for transport to the sand supply of the foundry. During the subsequent or second stage, the machine is activated for blast cleaning as the castings continue to tumble. During the latter stage, the aforementioned gate is operated to cut out the first named separators whereby all of the magnetic abrasive and residual sand from the cleaning chamber is displaced to another separator system which removes residual sand and spent abrasive and recovers re-usable abrasive or shot for recycle to the blast machines preferably in the form of centrifugal throwing wheels.

It is a principal object of this invention to provide an apparatus for the combination of rough cleaning and finish cleaning foundry castings wherein such foundry castings can be introduced directly into the apparatus without requiring an initial shake-out operation and it is a related object to provide a method and apparatus of the type described for cleaning foundry castings in a manner which enables a substantial increase in operating capacity.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, the invention will be described with reference to the accompanying drawing.

Included within the assembly is a device for continu ously tumbling the castings and for directing blast media onto the castings while being tumbled. A device of the type described is marketed by The Wheelabrator Corporation under the trademark Tumblast and is more fully described in US. Pats. No. 2,909,012 and No. 2,918,758. Briefly described, it embodies an enclosure 1 having a movable door 2 for gaining access to the interior of the enclosure. An endless belt 4 in the form of metal slats is guided for movement in one direction about idler rollers and guides to provide a concave pocket adapted to support the castings 3 and when loaded into the device as by means conventional to the trade such that detailed description thereof need not be given.

One or more centrifugal throwing wheels 6 are mounted in the upper portion of the enclosure for tthrowing pellets of abrasive downwardly onto the castings 3 as they are being tumbled within the enclosure to enable the centrifugally thrown abrasive particles to gain maximum access to the surfaces and innermost regions of the castings.

The spent media and debris passes downwardly through a preliminary screening arrangement, such as a screen 8, into a collecting trough 7 at the bottom of the housing for conveyance rearwardly from the housing by a screw 70. The conveyor is continuously operated by an electrical motor 9 and the spent media and debris is discharged into an elevator 10, which may be of the endless bucket type, having any suitable driving means 11 for operation thereof. The elevator 10 discharges the material into a chamber 12 having an opening 14 in the bottom wall in communication with a chute 20 with a gate member mounted for rocking movement adjacent the opening for operation between open and closed positions. The gate 15 is actuated between open and closed positions by an arm 16 which may be manually operated or operated by an electric motor 17 or air cylinder controlled by any suitable time cycle switch 18 for timed operation of the gate between open and closed positions.

In the illustrated open gate position, the discharge from the elevator 10 falls through the opening 14 into the chute 20 to one end portion of a screw conveyor 21. When the gate is closed, the discharge is displaced laterally from the housing 12 by a screw conveyor 22. The conveyors 21 and 22 feed separators 23 and 24 respectively. Separator 24 is of the air wash type illustrated and which is described in fuller detail in US. Pat. No. 3,005,547, while separator 23 may also be of similar construction. Briefly stated, such separators include a scalping screen 25 which separates coarse debris for lateral displacement to a chute 26 while sand or fine refuse discharges through spout 27 which delivers the sand or refuse to the dump or reservoir via a conveyor, not shown. The separator 24 also includes outer flights 40 for spreading the outflowing material across a bafile 41 and then to a discharge chute which delivers usable blast media into hopper 28 which communicates with the inlet to the centrifugal wheel 6 with a manually or automatically operated gate 30 in the passage to control the return of the blast media to the blast machine. The outer flights and baffle 41 are not necessary in the absence of magnetic separation.

A preferred form of blast media comprises shot or grit formed of magnetic material such as iron or steel. The separator 23 has a scalping screen 42 which separates large size waste for discharge to the waste discharge 32. The fine material, including spent and reclaimable blast media falls through screen 42 and is spread laterally by outside flights 31 across baffle 43 and then falls onto the magnetic drum separator 33. Non-magnetic material, such as foundry sand, etc. falls from the magnetic drum into chute 34 for disposal to the foundry sand reservoir or the like. The separated magnetic material is delivered to the hopper 35 for passage through the conduit 36 to the conveyor 7 beyond the blast housing.

The following will illustrate the operation of the systern embodying the features of this invention. When the door is open, the tumbler 4, conveyors 7, 10 and 21, separator 23 and the magnetic separator 33 are operated with the gate 15 in open position. A first load of work, which comprises castings and substantially all of the molding sand and core material, is dumped into the tumbler 4, a second load a short time thereafter, such as 6 minutes thereafter, and a third load a corresponding increment after the second, whereby a number of loads are sequentially introduced into the machine with the majority of the sand and debris removed before the subsequent load is introduced thereby to minimize the burden imposed upon the machine while increasing its capacity. During the first increment of time, the first load of work pieces is shaken out by the tumbler 4. The debris, including the foundry sand, core material and gating and the like, which separates from the castings, passes through the screening member 8 into the conveyor 7 for discharge to the elevator 10. The waste is delivered at the top by the elevator 10, falls through the gate 15 and the chute 20 to the conveyor 21 for lateral displacement into the separator 23. The large debris is separated from the fine material by the scalping screen 42 and is discharged to the waste outlet 32 for disposition. The fines pass on to the magnetic separator 33. The separated non-magnetic sand and the like falls into the outlet 34 while the magnetic material is recycled through the chutes 35 and 36 to the conveyor 7. At the end of the first period of operation, the first load has been roughly cleaned and the machine is prepared for the second load, etc. The second, third, etc. loads may add somewhat to the accumulation of the small size magnetic debris but, generally speaking, all of the unwanted debris from the combined rough cleaning operations is sequentially disposed of through the waste outlet 32 with the sand and fine refuse through the outlet 34. It Will be apparent that although. the machine handles increasing volumes of castings, the sand and waste load is only nominally increased per load.

At the end of the loading and cleaning operation, the fine cleaning period is initiated. Manually or automatically, the loading door 2 and the gate 15 are displaced to closed positions. The conveyor 22 and the blasting wheels 6 are placed into operation. The gate 30 is open for recycle of the blast media to the blasting machine 6. Conveyor 21 and separator 23 may remain in operation for an additional period of time to purge the units of residual debris.

During the fine cleaning operation, separator 24- removes sand which has escaped separation by the unit 23 and it also operates to separate the coarse debris which may be dislodged from the castings during the finish cleaning operation or otherwise remain from the previous operational cycle. Thus the metallic debris, including worn or fractured blast media, is separated from that which is reusable for return to the hopper 28 for recycle to the blast machine. The fine cleaning operation is completed in a short period of time, such as 10 minutes. Following a preferred though not essential short post tumbling period, the machine is shut down for unloading the cleaned work pieces.

In a typical cycle of operation, three loads are processed at 6 minute intervals to give a total of 74 molds in which the sand volume is 1.24 cubic feet per mold and the gated casting volume is 46 cubic feet per mold. The casting density, after sand removal, is of the order of pounds per cubic foot. At the end of the described three loading operations, 34 cubic feet of castings have been introduced into the Tumblast machine and substantially all of the sand volume has been removed from the loads introduced. The respective separations will return to the foundry sand reservoir the major portion of the approximately 92 cubic feet of sand which is reusable, the balance being non-reusable burned in sand and core sand which is removed from the castings during the blasting operation. The recovered sand is cleaned and otherwise conditioned for return to the molding floor.

The number of loads, the volume of the loads and the time cycles given in the foregoing description are provided only by way of illustration and not by way of limitation. It will be understood that a cycle may include one or more loads and that the time sequence can be varied quite broadly, depending somewhat upon the volume of materials and the characteristics of the castings, sand and blast media employed. More than one blasting wheel may be employed and use can be made of blast media other than steel shot or grit, although preferably of a separate magnetic material.

It will be further understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A machine for rough cleaning sequentially introduced loads of work pieces such as castings contained in foundry molds and then finish cleaning the sequentially introduced work pieces in a continuous operation, comprising a chamber for receiving the contents of said foundry molds, means within said chamber to support and tumble said contents, a centrifugal blast machine within said chamber to bombard the tumbling work pieces with blast media, a first conveyor communicating with said chamber to receive therefrom sand and debris from said work pieces during tumbling of said sequentially introduced loads of work pieces, a second conveyor communicating with said first conveyor, a first separator to receive debris directly from said second conveyor to eflect a separation of unwanted trash from said sand and debris, a second separator in direct communication with the first separator to receive the residue therefrom and remove the sand content thereof, a third separator adapted to separate reusable blast media from sand and spent blast media, a third conveyor communicating between said first conveyor and said third separator, valve means for controlling flow from said first conveyor optionally to said first or third separators, and means communicating between said third separator and said blast machine for return of reusable blast media recovered in said third separator.

2. A machine as claimed in claim 1 in which the blast media comprises magnetic metal particles and in which the second separator is a magnetic separator for removal of magnetic metal particles from the remainder.

3. A machine as claimed in claim 1 in which the third separator is of the air wash type.

References Cited UNITED STATES PATENTS 3,005,547 10/1961 Freeman 20932 3,097,450 7/1963 Freeman et al. 5113 3,097,451 7/1963 Freeman et al. 51-13 3,097,452 7/1963 Freeman et al. 5113 3,103,766 9/1963 Freeman et al. 5113 LESTER M. SWINGLE, Primary Examiner US. Cl. X.R. 

